doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Beretta 686 barrel trunnion hex key size

Does anyone know the size of the metric hex key used to tighten/remove the barrel trunnion on a 686? Thanks.

4mm

Thank you Bluestem. You just made things a little easier.

I've been shooting my 682 regularly in competition and daily practice since about 1985 and it is still tight. Is your 686 loosening up or are you messing with the trunnions for some other reason?

Is it a simple procedure to replace the trunnions? Screw the old ones out and screw in the new ones? No gunsmith needed?
I have 2 Beretta's and they are both tight. But, I've wondered how to replace the trunnions if needed.
Bill

The trunnions (i.e. hinge pins) must be fitted to the barrel monoblock slots. Simply swapping in larger pins without proper fitting will compromise the lockup. The hinge pins, however, rarely need to be changed. Changing to the next size locking bolt (a $35 part) is usually enough to tighten up the 680 action.

I was shooting the gun on Tuesday and as was holding the open gun in my hand. My fingers felt an unusual edge on the receiver. What I found was the lip of the right trunnion protruding from the side of the receiver. I dismounted the barrels and saw the flange that the barrels pivot on to be half the width of the other trunnion. It became obvious that the right trunnion was backing out. I discontinued shooting.

I own three 686 guns in various gauges. I’ve had them for decades. This was the first time I experienced anything like this and consider it anomalous. Additionally, I’ve casually investigated the matter now and it appears that this rarely happens. I presume that the trunnion when installed was not as tight as all the other 686s made.

I’m not unhappy or irritated by it. I understand that things happen to everything.

I guess using loctite and really torqueing down on the trunnion should solve the problem. First time I've heard of that happening.

It just goes to show how easily it is to replace worn trunnions. While unintended, it's a good reminder. There's a TGS video where Jonny extols the ease of stripping down the 686 with a simple tool and that replacement parts are easily installed and inexpensive. In his case, a Leatherman was used by him to break it down. Gil

Thanks, Bluestem for your comments. I doubt that I will shoot my field grade 687EELL enough to shoot it loose. But, it is comforting to that the trunnions are replaceable without too much trouble.